Flat plate traveling roller imaging system

ABSTRACT

A photoelectrophoretic imaging machine employing a stationary electrode over which two imaging and one transfer roller electrode travels to form and transfer an image formed from photoelectrophoretic ink exposed to light and subjected to electric field. The roller electrodes are journaled in two separate carriages with one drive mechanism employed to propel the carriages and a second drive mechanism employed to rotate the roller electrodes. The roller electrodes are lowered into contact with the stationary electrode by an elevator mechanism that enables the forces exerted on the roller to be varied from one end of a roller to the other. Means are provided for loading and ejecting a record sheet from the surface of the transfer roller. An auxiliary drive mechanism and cleaning station are positioned to engage the imaging roller electrodes after they pass over the stationary electrode.

United States Patent Egnaczak et al.

[54] FLAT PLATE TRAVELING ROLLER IMAGING SYSTEM [72] Inventors:Raymond-K. Egnaczak, Williamson; Gino F. Squassoni, Pittsford, both ofNY.

[73] Assignee: Xerox Corporation, Rochester, N.Y.

[22] Filed: Nov. 14, 1969 211 App]. No.: 876,848

gllll Primary Examiner-Samuel S. Matthews Assistant Examiner-Robert P.Greiner Attorney-James J. Ralabate, David C. Petre and Michael H.

Shanahan [57] ABSTRACT A photoelectrophoretic imaging machine employinga stationary electrode over which two imaging and one transfer rollerelectrode travels to form and transfer an image formed fromphotoelectrophoretic ink exposed to light and subjected to electricfield. The roller electrodes are joumaled in two separate carriages withone drive mechanism employed to propel the carriages and a second drivemechanism employed to rotate the roller electrodes. The rollerelectrodes are lowered into contact with the stationary electrode by anelevator mechanism that enables the forces exerted on the roller to bevaried from one end of a roller to the other. Means are provided forloading and ejecting a record sheet from the surface of the transferroller. An auxiliary drive mechanism and cleaning station are positionedto engage the imaging roller electrodes after they pass over thestationary electrode.

19 Claims, 6 Drawing Figures PATENTEnmzz I972 3,644,035

SHEET 1 [IF 4 I N VENTORS RAYMOND K. 56 CZAK BY NO SW ATTORNEYPATENIEDFEB22 m2 3, 644,035

SHEET 2 UF 4 FIG. 2

PATENTEDFEB 22 I972 SHEET R []F 4 BACKGROUND OF THE INVENTION Thisinvention relates generally to an imaging system and in particular to aphotoelectrophoretic imaging system. More specifically, the inventionrelates to new and improved methods and apparatus for implementing thephotoelectric imaging process.

In the photoelectrophoretic imaging process, an image is formed from animaging suspension or ink by subjecting the ink to an electric field andexposing it to activating electromagnetic radiation, e.g., visiblelight. The imaging suspension is comprised of photosensitive particlessuspended within an insulating liquid carrier. The particles arebelieved to bear a net electrical charge while in suspension. Normally,the ink is placed between injecting and blocking electrodes used toestablish the electric field and is exposed to a light image through oneof the electrodes which is at least partially transparent. According toone theory, particles attracted to the injecting electrode by theelectric field exchange charge with the injecting electrode when exposedto light and migrate under the influence of the field through the liquidcarrier to the blocking electrode. As a result of the migration,positive and negative images are formed on the two electrodes. Theblocking electrode is.covered with a dielectric material to preventcharge exchange with the particles and thereby prevent the particlesfrom oscillating back and forth between the two electrodes.

The photoelectrophoretic imaging process is either monochromatic orpolychromatic depending upon whether the light-sensitive particleswithin the liquid carrier are responsive to the same or differentportions of the light spectrum. A full-color polychromatic system isobtained, for example, by using cyan, magenta and yellow-coloredparticles which are responsive to red, green and blue lightrespectively. An extensive and detailed description of thephotoelectrophoretic process is found in U.S. Pat. Nos. 3,384,565 and3,384,488 to Tulagin and Carreira, 3,383,993 to Yeh and 3,384,566 toClark.

The photoelectrophoretic imaging system disclosed in theabove-identified patents utilizes a transparent flat plate configurationfor one of the electrodes used in establishing the electric field acrossthe imaging suspension. However, these patents do not discuss an imagingsystem adapted for the rapid production of images in a sequential manneras is desirable for a commercial application of the photoelectrophoreticprocess.

The present imaging system employs a stationary flat plate electrodeover which first and second imaging roller electrodes are passed to forman image from photoelectrophoretic ink present between the electrodes.The image formed from the ink is transferred to a record sheet loadedonto the surface of a transfer roller electrode and passed over thestationary electrode. The roller electrodes are mounted on carriageswhich are shuttled back and forth over the stationary electrode by noveldrive means permitting the rapid and efficient formation of a pluralityof images. The imaging and transfer roller electrodes are coupled totheir respective carriages by elevator mechanisms. Each elevatormechanism can vary the elevation of a roller relative to the stationaryelectrode over a continuous range and can position the ends of a rollerat different elevations. These abilities enable the elevator mechanismsto vary the shape of the interface or nip between a roller and thestationary electrode. Image formation and transfer occurs substantiallyin the nip and controlling its shape helps control the image forming andtransferring operations. Furthermore, a novel auxiliary drive mechanismis used in combination with separate cleaning assembly to clean thesurfaces of the imaging roller electrodes.

Accordingly, it is an object of the present invention to improvephotoelectrophoretic imaging systems.

More specifically, it is an object of the invention to devise novelapparatus for effecting the rapid and efficient production ofphotoelectrophoretic images using traveling roller electrodes and astationary flat plate electrode.

Another object of the invention is to devise novel means and methods forcompressing the injecting and blocking electrodes of aphotoelectrophoretic imaging system.

Another object of the invention is to control the configuration of thenip between injecting and blocking electrodes of a photoelectrophoreticimaging system.

Another object of the invention is to devise novel means for effectingtranslation and rotation of a roller electrode used in aphotoelectrophoretic imaging machine.

Yet another object of this invention is to devise novel means forhandling a record sheet to which a photoelectrophoretic image istransferred.

DESCRIPTION OF THE DRAWINGS Other objects and features of the presentinvention will be apparent from a further reading of the instantdescription of the invention and the drawings which are:

FIG. 1 is a perspective view of a photoelectrophoretic imaging machineaccording to the present invention;

FIG. 2 is a cross-sectional elevation view of the imaging machine takenalong lines 2-2 in FIG. 1;

FIG. 3 is a schematic illustration of a sheet-handling system in sideelevation and the transfer roller electrode used in the machine of FIG.1;

FIG. 4 is a side elevation view of the auxiliary drive mechanism used bythe machine of FIG. 1;

FIG. 5 is a perspective isolated view of the drive mechanism forpropelling the carriages used by the machine of FIG. 1; and

FIG. 6 is a perspective isolated view of a rotational gear rack andassociated apparatus used with the transfer roller on the machine ofFIG. 1.

DESCRIPTION OF THE INVENTION roller electrode 3 is a blocking electrodeof conventional design having a conductive core overcoated with anelectrically insulating material. An image is formed on the stationaryelectrode by coating the roller electrode 3 or the stationary electrode2 with a photoelectrophoretic ink and by passing the roller electrodeover the stationary electrode. Typically, the stationary electrode iselectrically grounded and the roller electrode is coupled to voltagesource of at least :L-3,000 volts, as an example. The electric fieldestablished between the electrodes by the voltage potentials causes thephotosensitive ink particles exposed to light to migrate away from thestationary electrode. The ink particles remaining on the stationaryelectrode form the desired image. The ink is exposed to electromagneticradiation to which it is responsive, such as visible light, through thestationary electrode by means of the exposure mechanism 5.

Roller exposure 7 is also a blocking electrode being composed of anelectrically insulating material overcoating a conductive inner core.This second roller electrode 7 is passed over the stationary electrodein the same manner as the first roller electrode 3. The second roller isalso coupled to a highvoltage source but not necessarily of the samepotential. The second roller is not coated with ink but is used as ameans to subject to a field the ink subjected to a field during thepassage of the first roller electrode. This subsequent subjection of theink to an electric field is accomplished by exposure of the ink to lightand is found to improve the quality of the image.

The image formed on the stationary electrode is transferred to arecording sheet by means of the transfer roller electrode 8. The sheetis typically a paper material made from cloth or wood fibers and of aquality selected to suit the needs of a particular user. The details ofthe sheet-feeding mechanism are not shown in FIG. 1 in order to simplifythat drawing. FIG. 4 illustrates schematically the details of thesheet-handling apparatus which are discussed in more detail later. Thetransfer roller electrode is-also a blocking electrode comprising anelectrically insulating layer over a conductive core. A portion of thecylindrical roller is cut away as indicated in FIG. 3 to accommodateloading and unloading a sheet around the periphery of the roller. Againthis is discussed in more detail later. The image is transferred to thesheet by coupling a high voltage to the transfer roller of a polarityopposite to that coupled to the first and second rollers 3 and 7. Thefield established between the transfer and stationary electrodes istherefore such to effect the migration to the sheet of all the inkparticles forming the image. The foregoing operation takes place as thetransfer roller is passed over the image.

The transfer of an image is normally made in the absence of light.Imagewise light, i.e., light in the same configuration as used to formthe image, can be used in the transfer operation without making anysubstantial alternations to the system. If white light, i.e., radiationincluding all wavelength to which the ink is exposed, is used thepolarity of the voltage coupled to the transfer electrode is changed tobe the same as that coupled to the first and second roller electrodes.It is noted that the present machine is particularly adapted for the useof light during transfer of an image. This is true for any type ofillumination or exposure means employed whether full frame or scan typeor using transparency or opaque originals. The reason is that imagetransfer takes place substantially at the same locations as imageformation. Consequently, no particular mechanical alternation need bemade to the exposure mechanism or other parts of the system to makelight available during transfer.

Machine 1 includes a frame 9 on which the stationary electrode 3 isrigidly' supported. The imaging roller electrodes 3 and 7 are journaledfor rotation in carriage while the transfer roller electrode 8 isjournaled for rotation in carriage 11. Carriages 10 and 11 are slidablysupported on the frame 9, as shown in FIG. 2, by the rails 13, 14, 15and 16 and an appropriate number of wheels of which the wheels 17, l8,l9 and are typical. Wheels 17 and 19 are rotatably coupled to thecarriages for rotation about a horizontal axis and ride in tracks 13 and15 to stabilize the carriages in a vertical plane. Wheels 18 and 20 arerotatably coupled to the carriages for rotation about a vertical axisand ride in tracks14 and 16 to stabilize the carriage in a horizontalplane.

The carriages include bearing mounts 21-26 (FIG. 1) mounted on eitherside of the carriages for raising and lowering the rollers 3, 7 and 8.The bearing mounts constitute an elevator mechanism for moving therollers between an elevation atwhich they contact the stationaryelectrode and an elevation at which they clear the stationary electrode.In addition, each bearing mount operates independently so the ends of aroller can be positioned at a different elevation from the stationaryelectrode. The bearing mounts, of which mounts 25 and 26 in FIG. 2 'aretypical, are coupled to the walls of the carriages by coil springs 29and the fluid-operated cylinders 30. The axle 31 of a roller electrode,e.g., roller 3, is journaled by a bearing 32 in the plate 33 made froman electrically insulating material. A voltage potential is coupled to aroller electrode through its axle by means of an electrical lead 35 anda conductive brush 36 that rides on the surface of an axle.

The insulating plate 33 is coupled to springs 29 and a cylinder with thesprings acting as a mechanical bias that forces the plate 33 upward tohold a roller at an elevation out of contact with the stationaryelectrode. The cylinder barrel 37 is coupled to the wall of a carriageand the piston rod 38 is coupled to a plate 33. The springs 29 force thepiston rod up into the barrel to expel any fluid in the cavity behindthe piston 38 through the orifice 39. The orifice is coupled byappropriate valves and pumping to a fluid pump which pumps a fluid intothe cylinder to extend the piston rod. The extended piston rod in turnforces the plate 33 downward compressing spring 29. The stroke of thepiston, i.e., the distance it moves downward, is selected to move thebearing mount and therefore theroller into contact with the stationaryelectrode.

The roller electrodes 3, 7 and 8 are compressible at least to somedegree so that when forced downward against the stationary electrodethey flatten over some finite area hereafter referred to as a nip. Imageformation and transfer takes place substantially in the nip because, forone reason, that is the area in which the electric field is thestrongest. The elevator mechanism, i.e., the cylinders, enable thegeometry of the nip to be conveniently varied to effect some variationin an image either during formation or transfer of the image. The widthof the nip is varied by uniformly increasing or decreasing the fluidpressure in the cylinders at opposite ends of a roller. The nip can berendered substantially trapezoidal or triangular by making the fluidpressure in a cylinder at one end of a roller greater than that in thecylinder at the other end of a roller.

The cylinders 30 on the left and right sides of a roller electrode aresqueeze means for controlling the force exerted between roller andstationary electrodes. The force exerted between the electrodesestablishes the shape of the nip between them. The force and thereby nipshape is controlled by varying the fluid pressure inthe cylinders. Thefluid may be either a gas or a liquid and its pressure is controlled byan appropriate valve or other fluid pressure control device such as avariable displacement pump. The fluid-operated cylinder providesexcellent force control over a continuous range of forces. In addition,since the piston rod of a cylinder extends when the load is moved, thefluid-operated cylinders 30 also provide means for insuring constant anduniform forces between the roller and stationary electrodes.

The carriages are propelled past the stationary electrode betweenstarting or park positions on the left side of electrode 2 (FIG. 1) andturn positions on the right side of electrode 2. The drive mechanism forpropelling the carriages (FIG. 5) include the drive rack gears 43 and 44which are rigidly coupled to carriages l0 and 11 respectively andslidably supported on frame 9. The gears 45 and 46 mate with the driveracks 43 and 44 respectively to propel the drive racks and therefore thecarriages back and forth along the frame. Gears 45 and 46 are powered byelectric motors 49 and 50 respectively to which they are coupled byappropriate shafts 47 and 48 and appropriate gear mechanisms 51 and 52respectively.

The roller electrodes 3, 7 and 8 are rotated at an angular velocity toestablish substantially a zero relative velocity between points on theperipheries of the rollers and points on the surface of the stationaryelectrode 2. The zero relative velocity between roller and stationaryelectrodes prevents ink from being smeared or otherwise adverselyaffected by the rollers. Each roller is rotated by a gear and rackassembly typical of which is the gear and rack assembly for the firstroller electrode 3 shown in FIG. 2. The diameter of the rollers, speedof the carriages and gear ratios are selected to obtain the desired zerorelative velocity. The rotational rack gears 55, 56 and 57 are coupledto the frame 9 being braced against sliding movement and biased by coilsprings 58 upward into contact with a mating pinion gear, of which gear59 for roller 3 is typical. The spring mounts for the rotational driveracks enable them to remain engaged with the mating pinion gears (suchas gear 59) whether or not the rollers are positioned by the elevatormechanisms at an elevation for contacting or clearing the stationaryelectrode.

The rotational pinion gears, e.g., gear 59, are coupled to the axle of aroller, e.g., axle 31, by means of an override clutch, e.g., clutch 62.The override clutch is functionally equivalent to a ratchet and pawlmechanism where a circular ratchet is coupled to the axle 31 and thepawl is coupled to a gear such as gear 59. The pawl engages a tooth onthe ratchet when carriages l0 and 11 move from the park to the turnpositions causing a roller to be rotated. The pawl slides over the teethon the ratchet when the carriages travel from the turn to the parkpositions preventing rotation of a roller. The gear cou pled to theroller, e.g., gear 59, is rotated during the turn to park travel becauseit is always operatively engaged with the rotational rack gear, e.g.,rack gear 56. However the override clutch disengages a gear, e.g., gear59, from an axle, e.g., axle 31 during the turn to park travel.

The rotational rack gear 55 used to rotate the transfer roller includesan additional feature. The rack gear 55 is normally braced againstsliding movement relative to the frame 9. However, the shorten theoverall length of machine 1, the rack is coupled to fluid-operatedcylinder 63 (FIG. 6) which pulls the rack 55 toward the park positionafter carriage 11 has traveled past the stationary electrode and come toa stop. The circumference of the transfer roller is sufficiently largeto have an entire image on the stationary electrode transferred to asheet on its surface when it has been rotated less than 360. Once theimage is transferred to the sheet the carriage can stop. However, toeject the sheet from the transfer roller it must be rotated through anadditional angular displacement. The transfer roller is rotated theadditional amount by pulling the rack gear 55 back toward the parkposition to rotate the pinion gear (similar to gear 59) coupled throughan override clutch (similar to clutch 62) to the axle (similar to axle31) of the transfer roller 8.

Referring now to FIG. 6, the rack gear 55 is supported by bias springs58 above the slide member 64. Member 64 is supported for slidingmovement relative to frame 9. The piston rod 66 of cylinder 63 iscoupled by appropriate means to the slide member 64 and is normallysubstantially fully extended out of barrel 65. A fluid is pumped intothe cylinder barrel 65 via conduit 67 to force the piston rod and slidemember to the left, i.e., toward the park piston. This movement of theslide member 64 effects the ejectment of a sheet from the transferroller to an output tray. Thereafter, a fluid is pumped into thecylinder barrel 65 via conduit 68 to return'the rack member to itsstarting position. This movement of the rack 55 toward the turn positiondoes not rotate the transfer roller 8 because of the override clutch(such as clutch 62) coupled to the axle of the transfer roller.

The sheet-handling apparatus associated with the transfer roller isschematically illustrated in FIG. 3. An input tray 70 supports the stackof sheets 71. The top sheet in the stack is fed to the buckle mechanismcomprising the buckle cams 72 and the release cam 73. Cam 72 is afriction device which is normally rotated to the portion shown to permita sheet to be fed onto the table 74. The sheet fed onto the table isrestrained from further advancement by the stop pad 75 on the releasecam 73. The buckle cam 72 is then rotated counterclockwise substantially360. The cam 72 engages the sheet fed onto the table and forces itagainst the stop pad 75 causing it to buckle in the manner shown.Meanwhile, the transfer roller 8 is rotated until the gripper fingers 78are positioned near the release cam 72. The fingers 78 are mounted on ashaft 79 that is appropriately torque biased to maintain the gripperfingers closed, i.e., in contact with the periphery of the roller. Atrip device 80 is rigidly coupled to the shaft and rotates the shaftclockwise against the bias when an interposer member 81 is placed in itspath. The interposer 81 is a shaft coupled to the piston rod of acylinder. The cylinder is coupled to the carriage and is positionedrelative to the trip device 80 to place the interposer in the path ofthe trip device when the piston rod is extended. The interposer ispositioned relative to the transfer roller to open the gripper fingers(i.e., move them to the position shown) when they approach the releasecam.

The stop pad 75 is lifted to allow the buckled sheet to shoot forwardinto the open gripper fingers. Once the gripper fingers have rotatedwith roller 8 past the interposer 81, they close on the sheet. The sheetis pulled around the periphery of the roller by the gripper fingers withthe image on the stationary electrode being transferred to it in theprocess. The high-voltage potential coupled to the roller not onlyattracts the ink particles from the grounded stationary electrode butalso acts to electrostatically tack the sheet to the roller.

After the image is transferred to the sheet the carriage comes to a stopwith the roller 8 in substantially the same angular position as shown inFIG. 3. At this point cylinder 63 in FIG. 6 is activated to pull therack 55 toward the park position. Once again the interposer 81 isinserted into the path of the trip device 80 to open the gripperfingers. This time the gripper fingers are opened to release the sheeton the surface of the roller. The separator fingers 87 are normally atthe position shown and are coupled to shaft 88 which is in turnrotatably supported by carriage 11. The shaft 88 is rotated byappropriate means counterclockwise to lower the fingers into the cutout89 in the roller 8. The separator fingers deflect the sheet into thebite of friction feed rollers 90 which advance the sheet onto the outputtray 90a. The movement of rack 55 continues toward the park positionuntil the roller 8 returns to substantially that angular position shownin FIG. 3. The transfer roller remains in this angular position when thecarriage is returned to the park position because of the override clutch(like clutch 59) coupled to its axle and the gear (like gear 59) matedwith the rotation drive rack 55. A plurality of cam-operated switches 60(FIG. 5) are activated by the movement of the carriages to generateelectrical and mechanical timing signals for apparatus such as bucklecam 72, release cam 73 and interposer 81. The timing signals enable thevarious machine operations to occur at the proper instant in time.

The first and second imaging rollers 3 and 7 respectively have theirsurfaces cleaned by the cleaning assembly 91 when carriage 10 is atthe'turn position. The cleaning tank 92 contains a cleaning fluid(normally the same material as the insulating fluid used in thephotoelectrophoretic ink) and brush rollers 93 and 94. The rollers 93and 94 are journaled for rota tion in the tank 92 and are rotated byappropriate motors and drive means. The outer surface of each brushroller is a fiber material which is wetted by the cleaning fluid as thebrush rollers rotate. The tank 92 and brush rollers are raised by hoistmeans to an elevation at which the brush rollers 93 and 94 contact theimaging rollers 3 and 7 respectively. The rollers 3 and 7 are maintainedat their uppermost position by the cylinders 30 at this time.

The cleaning assembly includes the tank 92 which is slidably supportedby the standards 95 and 96. The threaded shaft 97 is engaged with matedthread in the floor of the tank. Motor 98 is coupled to shaft 97 byappropriate gear means 99 for rotating the shaft. The shaft is rotatedclockwise to raise the tank 92 and counterclockwise to lower it.

The imaging rollers 3 and 7 are rotated by the auxiliary drum mechanism10] shown in FIGS. 1 and 4 when carriage 10 is at the turn position. Theauxiliary drive mechanism has the concave members 102 and 103 coupled tothe piston rods of fluid-operated cylinders 104 and 105. The concavemembers 102 and 103 are extended into friction engagement with matingconvex members coupled to the axles of rollers 3 and 7 when carriage 10is at the turn position and the rollers are held at their highestelevation by the bias springs 29. Convex member 108 (FIG. 2) coupled toaxle 31 of the first imaging roller electrode 3 is typical of a likeconvex member coupled to the axle of the second imaging roller 7. Theconcave members 102 and 103 are rotated in the same direction theimaging electrodes are rotated when moving over the stationaryelectrode. The override clutch permits the axle of the rollers 3 and 7to be rotated without rotating the gears engaged with rotational rackgears 56 and 57.

The concave members 102 and 103 and associated apparatus aresubstantially identical and for this reason the description of onesuffices for the other. Accordingly, convex member 103 (FIG. 4) iscoupled to a keyed shaft 109 which is journaled for rotation in pillowblocks 10. The keyed shaft 109 has a groove extending parallel to itsaxis of rotation. The pulley 111 is coupled to shaft 109 by a key memberrigidly coupled to the pulley and slidably fit into the groove. The keymember on the pulley transmits the rotation of the pulley to the keyedshaft and permits shaft 109 to slide along its axes while being rotated.Accordingly, the concave member 103 can be slid into and out ofengagement with the convex member 108. The pulleys 111 are driven by anelectric motor 112 through appropriately connected pulley and beltsincluding pulley 113 and continuous belt 1 14. The keyed shaft 109 iscoupled to the piston rod 117 of cylinder 105. Cylinder is adouble-acting cylinder that extends piston rod 117 when a fluid ispumped into barrel 118 through orifice 119 and retracts the piston rodwhen fluid is pumped into the barrel through orifice 120.

The auxiliary drive mechanism 101 cooperates with the cleaning assemblyto remove unused ink and other materials from the surfaces of theimaging rollers 3 and 7, The concave members 102 and 103 are extendedand rotated to rotate the rollers 3 and 7. The cleaning tank 92 israised to bring the brush rollers 93 and 94 into contact with rollers 3and 7. The fiber material on the brush rollers wet and scrub thesurfaces of rollers 3 and 7. The cleaning assembly 91 and auxiliarydrive mechanism are retracted from the rollers after the cleaningoperation is over. Squeegees can be pressed against the surfaces of therollers 3 and 7 to remove any remaining cleaning fluid if so desired.

The inking of the stationary electrode and/or the first imagingelectrode can be accomplished by pouring a photoelectrophoretic ink ontothe surface of roller 3 or electrode 2 since both are accessible forthis purpose. Alternately, appropriate inking means can be placed neareither the park or the turn positions to mechanically coat the surfaceof the roller electrode with an ink. Typical means might include awetting roller such as the brush rollers 92 and 93 submerged in an inkbath and positioned to contact the roller 3. Also, such a mechanismcould be coupled to carriage in front of the roller 3 to coat theelectrode 2 with ink as the carriage travels over it.

The exposure mechanism 5 used to expose the ink between the roller andstationary electrodes (regardless how the ink arrived there) includesthe transparency projector 123 of conventional design and the planemirror 124. The projector includes means for holding a transparency, forilluminating the transparency, for collecting the radiation passingthrough the transparency and for focusing a light image of thetransparency onto the interface or nip between the roller and stationaryelectrodes. The projector and mirror are mounted on the frame with theprojector aimed generally at right angles to the path traveled by therollers 3, 7 and 8. This enables the projector to be positioned at aconvenient access location on the frame. in addition, the exposuremechanism is physically out of the way of the carriages and other movingparts and enables the overall machine size to be minimized.

The mirror 124 converts the right reading light image of a transparencyto a reverse reading light image. This results in the formation of areverse reading image on the stationary electrode (as viewed lookingdownward onto the stationary electrode). The reverse reading image isonce again right reading, however, after the image is transferred to asheet. and

What is claimed is:

l. imaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid roller and stationary electrode to electromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions,

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image; and,

elevator means for moving a roller electrode into contact with thestationary electrode as it travels thereby and for controlling the forceexerted by the roller electrode along its length on the stationaryelectrode.

2. The apparatus of claim 1 wherein said elevator means includes meansto hold a roller electrode at a first elevation relative to thestationary electrode and means for independently moving each end of aroller electrode from that first position.

3. The apparatus of claim 1 wherein said elevator means includes biasmeans for holding a roller electrode at an elevation out of contact withthe stationary electrode and first and second means coupled to each endof the roller electrode for moving an end of a roller electrode towardthe stationary electrode.

4. The apparatus of claim 1 wherein said elevator means includes leftand right bearing mounts between which a roller electrode is journaled,left and right bias means for urging the left and right bearing mountsrespectively away from the stationary electrode and left and rightsqueeze means for moving the left and right bearing mounts respectivelytoward the stationary electrode against the force exerted by the biasmeans.

5. The apparatus of claim 4 wherein said squeeze means includefluid-operated cylinders.

6. imaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid roller and stationary electrode to electromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions,

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for affecting formation and transfer of an image; and,

handling means for loading a sheet onto the surface of the transferroller prior to passing over the stationary electrode and for ejectingthe sheet from the roller after an image has been transferred to thesheet.

7. The apparatus of claim 6 wherein said sheet-handling means includesgripper means for holding a sheet to the transfer roller, input meansfor feeding a sheet into the gripper means and separator means fordeflecting a sheet released by the gripper means from the roller to anoutput tray.

8. The apparatus of claim 7 wherein said input means includes a bucklemeans for buckling a sheet against a stop and a release means for movingthe stop pad to allow the tension of a buckled sheet to advance thesheet to the gripper means.

9. The apparatus of claim 7 further including an input tray forsupporting a stack of sheets and means for feeding a single sheet fromthe stack to the buckle means.

10. imaging apparatus comprising 7 a stationary transparent electrodeand at least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid roller and stationary electrode to elec tromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions; and,

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image, wherein saidrotational drive means includes means to rotate said transfer rollerafter it has traveled past the stationary electrode for ejecting fromthe transfer roller a record sheet to which an image has beentransferred.

11. lmaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid r oller and stationary electrode to electromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions, and

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image, wherein saidtranslational drive means includes at least one carriage supported fortravel past said stationary electrode and means for stabilizing thecarriage in horizontal and vertical planes.

12. The apparatus of claim 11 wherein said translational drive meansfurther includes rack gears rigidly coupled to said carriage andsupported for movement upon rotation of a pinion gear operativelyengaged therewith.

13. lmaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid roller and stationary electrode to electromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions,

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image, wherein saidrotational drive means includes first and transfer rack gears supportedadjacent the stationary electrode and operatively engaged with piniongears coupled to said at least first electrode and transfer rollerelectrode respectively by override clutches that permit rotation of aroller during park to turn travel.

14. The apparatus of claim 13 further including elevator means forvarying the elevation of a roller electrode relative to the stationaryelectrode and bias means for maintaining engagement between a pinion andrack gear for rotating a roller regardless of the elevation of theroller electrode.

15. The apparatus of claim 13 wherein said rotational drive meansfurther includes means for pulling said transfer rack gear toward thepark position after the transfer roller has traveled past saidstationary electrode for ejecting a record sheet from the transferroller after an image has been transferred thereto.

16. Imaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions,

exposure means for exposing photoelectrophoretic ink applied betweensaid roller and stationary electrode to electromagnetic radiation inimagewise configuration to form an image on the stationary electrodefrom ink exposed to radiation and subjected to an electric fieldestablished between the electrodes,

a transfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller,

translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions,

rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image; and,

cleaning means positioned adjacent said turn position to clean the firstroller electrode after the formation of an image.

17. The apparatus of claim 16 further including auxiliary drive meansfor rotating said first roller electrode independently of saidrotational drive means for assisting the cleaning means in cleaning thefirst roller electrode.

18. The apparatus of claim 16 wherein said rotational drive means forrotating said first roller electrode includes an override clutch andsaid auxiliary drive means includes a first friction member slidably androtatably supported for engaging a second friction member coupled tosaid first roller electrode for rotation of the roller electrode in adirection permitted by the override clutch.

19. In a photoelectrophoretic imaging system of the type wherein rollerand second electrodes are supported for relative movement to form animage from photoelectrophoretic ink present in the nip formed betweenthe electrodes exposed to electromagnetic radiation and subjected to anelectric field established by voltages coupled to the electrodes, anelevator mechanism for controlling the shape of the nip between theelectrodes comprising bias means to hold one electrode at a firstelevation relative to the other,

i left and right squeeze means coupled to the ends of one electrode toforce the electrodes together against the force of the bias means,

said bias means coupled to left and right bearing mounts supporting saidroller electrode urging the roller electrode to an out of contactelevation with the second electrode and wherein said left and rightsqueeze means include fluid operated cylinders coupled to the left andright bearing mounts respectively to force the roller and secondelectrodes into contact.

1. Imaging apparatus comprising a stationary transparent electrode andat least a first roller electrode supported for travel past thestationary electrode between park and turn positions, exposure means forexposing photoelectrophoretic ink applied between said roller andstationary electrode to electromagnetic radiation in imagewiseconfiguration to form an image on the stationary electrode from inkexposed to radiation and subjected to an electric field establishedbetween the electrodes, a transfer roller electrode supported for travelpast the stationary electrode over substantially the same path traveledby said first roller electrode to transfer an image formed on thestationary electrode to a record sheet carried by the transfer roller,translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions, rotational drive means forrotating said at least first roller electrode only as it travels pastthe stationary electrode from park to turn positions for effectingformation and transfer of an image; and, elevator means for moving aroller electrode into contact with the stationary electrode as ittravels thereby and for controlling the force exerted by the rollerelectrode along its length on the stationary electrode.
 2. The apparatusof claim 1 wherein said elevator means includes means to hold a rollerelectrode at a first elevation relative to the stationary electrode andmeans for independently moving each end of a roller elEctrode from thatfirst position.
 3. The apparatus of claim 1 wherein said elevator meansincludes bias means for holding a roller electrode at an elevation outof contact with the stationary electrode and first and second meanscoupled to each end of the roller electrode for moving an end of aroller electrode toward the stationary electrode.
 4. The apparatus ofclaim 1 wherein said elevator means includes left and right bearingmounts between which a roller electrode is journaled, left and rightbias means for urging the left and right bearing mounts respectivelyaway from the stationary electrode and left and right squeeze means formoving the left and right bearing mounts respectively toward thestationary electrode against the force exerted by the bias means.
 5. Theapparatus of claim 4 wherein said squeeze means include fluid-operatedcylinders.
 6. Imaging apparatus comprising a stationary transparentelectrode and at least a first roller electrode supported for travelpast the stationary electrode between park and turn positions, exposuremeans for exposing photoelectrophoretic ink applied between said rollerand stationary electrode to electromagnetic radiation in imagewiseconfiguration to form an image on the stationary electrode from inkexposed to radiation and subjected to an electric field establishedbetween the electrodes, a transfer roller electrode supported for travelpast the stationary electrode over substantially the same path traveledby said first roller electrode to transfer an image formed on thestationary electrode to a record sheet carried by the transfer roller,translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions, rotational drive means forrotating said at least first roller electrode only as it travels pastthe stationary electrode from park to turn positions for affectingformation and transfer of an image; and, handling means for loading asheet onto the surface of the transfer roller prior to passing over thestationary electrode and for ejecting the sheet from the roller after animage has been transferred to the sheet.
 7. The apparatus of claim 6wherein said sheet-handling means includes gripper means for holding asheet to the transfer roller, input means for feeding a sheet into thegripper means and separator means for deflecting a sheet released by thegripper means from the roller to an output tray.
 8. The apparatus ofclaim 7 wherein said input means includes a buckle means for buckling asheet against a stop and a release means for moving the stop pad toallow the tension of a buckled sheet to advance the sheet to the grippermeans.
 9. The apparatus of claim 7 further including an input tray forsupporting a stack of sheets and means for feeding a single sheet fromthe stack to the buckle means.
 10. Imaging apparatus comprising astationary transparent electrode and at least a first roller electrodesupported for travel past the stationary electrode between park and turnpositions, exposure means for exposing photoelectrophoretic ink appliedbetween said roller and stationary electrode to electromagneticradiation in imagewise configuration to form an image on the stationaryelectrode from ink exposed to radiation and subjected to an electricfield established between the electrodes, a transfer roller electrodesupported for travel past the stationary electrode over substantiallythe same path traveled by said first roller electrode to transfer animage formed on the stationary electrode to a record sheet carried bythe transfer roller, translational drive means for propelling said atleast first roller electrode and said transfer roller electrode pastsaid stationary electrode between park and turn positions; and,rotational drive means for rotating said at least first roller electrodeonly as it travels past the stationary electrode from park to turnpositions for effecting formation and transfer of an image, wherein saidrotational drive means includes means to rotate said transfer rollerafter it has traveled past the stationary electrode for ejecting fromthe transfer roller a record sheet to which an image has beentransferred.
 11. Imaging apparatus comprising a stationary transparentelectrode and at least a first roller electrode supported for travelpast the stationary electrode between park and turn positions, exposuremeans for exposing photoelectrophoretic ink applied between said rollerand stationary electrode to electromagnetic radiation in imagewiseconfiguration to form an image on the stationary electrode from inkexposed to radiation and subjected to an electric field establishedbetween the electrodes, a transfer roller electrode supported for travelpast the stationary electrode over substantially the same path traveledby said first roller electrode to transfer an image formed on thestationary electrode to a record sheet carried by the transfer roller,translational drive means for propelling said at least first rollerelectrode and said transfer roller electrode past said stationaryelectrode between park and turn positions, and rotational drive meansfor rotating said at least first roller electrode only as it travelspast the stationary electrode from park to turn positions for effectingformation and transfer of an image, wherein said translational drivemeans includes at least one carriage supported for travel past saidstationary electrode and means for stabilizing the carriage inhorizontal and vertical planes.
 12. The apparatus of claim 11 whereinsaid translational drive means further includes rack gears rigidlycoupled to said carriage and supported for movement upon rotation of apinion gear operatively engaged therewith.
 13. Imaging apparatuscomprising a stationary transparent electrode and at least a firstroller electrode supported for travel past the stationary electrodebetween park and turn positions, exposure means for exposingphotoelectrophoretic ink applied between said roller and stationaryelectrode to electromagnetic radiation in imagewise configuration toform an image on the stationary electrode from ink exposed to radiationand subjected to an electric field established between the electrodes, atransfer roller electrode supported for travel past the stationaryelectrode over substantially the same path traveled by said first rollerelectrode to transfer an image formed on the stationary electrode to arecord sheet carried by the transfer roller, translational drive meansfor propelling said at least first roller electrode and said transferroller electrode past said stationary electrode between park and turnpositions, rotational drive means for rotating said at least firstroller electrode only as it travels past the stationary electrode frompark to turn positions for effecting formation and transfer of an image,wherein said rotational drive means includes first and transfer rackgears supported adjacent the stationary electrode and operativelyengaged with pinion gears coupled to said at least first electrode andtransfer roller electrode respectively by override clutches that permitrotation of a roller during park to turn travel.
 14. The apparatus ofclaim 13 further including elevator means for varying the elevation of aroller electrode relative to the stationary electrode and bias means formaintaining engagement between a pinion and rack gear for rotating aroller regardless of the elevation of the roller electrode.
 15. Theapparatus of claim 13 wherein said rotational drive means furtherincludes means for pulling said transfer rack gear toward the parkposition after the transfer roller has traveled past said stationaryelectrode for ejecting a record sheet from the transfer roller after animage has been transferred thereto.
 16. Imaging apparatus comprising astationary trAnsparent electrode and at least a first roller electrodesupported for travel past the stationary electrode between park and turnpositions, exposure means for exposing photoelectrophoretic ink appliedbetween said roller and stationary electrode to electromagneticradiation in imagewise configuration to form an image on the stationaryelectrode from ink exposed to radiation and subjected to an electricfield established between the electrodes, a transfer roller electrodesupported for travel past the stationary electrode over substantiallythe same path traveled by said first roller electrode to transfer animage formed on the stationary electrode to a record sheet carried bythe transfer roller, translational drive means for propelling said atleast first roller electrode and said transfer roller electrode pastsaid stationary electrode between park and turn positions, rotationaldrive means for rotating said at least first roller electrode only as ittravels past the stationary electrode from park to turn positions foreffecting formation and transfer of an image; and, cleaning meanspositioned adjacent said turn position to clean the first rollerelectrode after the formation of an image.
 17. The apparatus of claim 16further including auxiliary drive means for rotating said first rollerelectrode independently of said rotational drive means for assisting thecleaning means in cleaning the first roller electrode.
 18. The apparatusof claim 16 wherein said rotational drive means for rotating said firstroller electrode includes an override clutch and said auxiliary drivemeans includes a first friction member slidably and rotatably supportedfor engaging a second friction member coupled to said first rollerelectrode for rotation of the roller electrode in a direction permittedby the override clutch.
 19. In a photoelectrophoretic imaging system ofthe type wherein roller and second electrodes are supported for relativemovement to form an image from photoelectrophoretic ink present in thenip formed between the electrodes exposed to electromagnetic radiationand subjected to an electric field established by voltages coupled tothe electrodes, an elevator mechanism for controlling the shape of thenip between the electrodes comprising bias means to hold one electrodeat a first elevation relative to the other, left and right squeeze meanscoupled to the ends of one electrode to force the electrodes togetheragainst the force of the bias means, said bias means coupled to left andright bearing mounts supporting said roller electrode urging the rollerelectrode to an out of contact elevation with the second electrode andwherein said left and right squeeze means include fluid operatedcylinders coupled to the left and right bearing mounts respectively toforce the roller and second electrodes into contact.